Electric winches are motorized pulling machines for moving heavy loads or towing vehicles with less effort than manual winches. Designed for intermittent use, they have a line that attaches to the load and a motor that rotates a drum to wind in the line and draw the load toward the winch. Industry safety standards call for a minimum of five wraps of line around the drum during pulls. Winches maintain their load capacity with up to two full layers of line wrapped on the drum, but capacity decreases with each additional layer. Electric winches rated for pulling are used for horizontal pulling or towing of loads. Electric winches rated for pulling and lifting can pull loads horizontally or lift and lower them vertically. DC winches are typically powered by a vehicle battery. AC winches plug into an electrical outlet for power.